Pekka Keskinen asked:
What is the smallest thing that is possible to see with a microscope?
Dave - It depends on the kind of microscope. Light behaves a bit like a wave. It has a wavelength. Itís very, very hard to see things smaller than the wavelength of the light because you essentially get interference effects. The waves interfere and it messes with your picture. With conventional microscopes itís very hard to see anything less than the wavelength of light which is about half a micrometer - roughly a 2000th of a millimetre. There are ways of doing things with light which means you can get a little bit smaller than that, using funky things called metamaterials, but they are not really common.
If you want to get much more magnification than that you need to use something with a much smaller wavelength. A common one to use is an electron, because although it appears like a particle itís also a wave and the wavelength is much, much shorter and therefore you can see much, much smaller things. You can actually see big atoms with a normal electron microscope. Other forms of microscope involve dragging a tip, itís called a scanning tunneling electron microscope, and you measure the electric current going between your tip and your object - with this, you can measure down to large atoms.
Chris - IBM iconically produced the letters IBM, I think it was 1990-1991, by manoeuvring Xenon atoms with a scanning tunnelling electron miscroscope didnít they? I canít remember quite many atoms they used, 40 or something, and it took them about 2 weeks to move these things around. People were saying this is the future of computing!
There was also a story that got published in the middle of 2008. It was by a researcher at the University of California, Berkley, Jannik Meyer. This was a wonderful paper because they were able to see hydrogen atoms. That probably qualifies as the smallest thing you could see because thatís the smallest entity at an atomic level in the Universe.
The way they did this was they had a sheet of graphene which is a single layer, one carbon atom thick, of graphite and they could drop molecules onto that surface and then scan across it with the scanning tunnelling electron microscope and measure where it was interacting. The tip was interacting with the different atoms.
Because the graphene is like a little pattern of chicken wire - itís a very regular hexagon pattern - itís very easy to subtract mathematically from whatever signature you pick up, so they can see any atomic species that were dropped on there. They could even see these little white dots that turned out to be hydrogen atoms; if you put a bigger molecule, like a butane molecule - the stuff that you burn in your lighter - on there, you can actually see this zig-zagging chain of hydrocarbons. Itís just absolutely phenomenal!
I think you can see smaller things that that by angling the stream of electrons you use to produce a effect on the object you observe? I read something about it but i don't remember where? It's more of an indirect observation due to what we already know of how 'matter' react to our microscope. Anyone that recognizes this? And we do have 'photos' of electrons(?) Well, their 'orbitals' at least. But the new thing in 'observing' is the idea of indirect observation where we due to known interactions can see if 'something' has changed some state, without us directly interfering with the object. This idea comes from the hope of us being able to 'go around' HUP (Heisenberg's uncertainty principle) and actually influence a particle without locking it into a certain 'state' by directly observing it, as well as getting knowledge of processes to small to observe directly by the waves we send from our microscope. What you want to see can't be smaller than the wavelength you use to look at it, so that puts a limit to what you can observe directly.
Yep, you're correct flr.
I think I found it, at last :)
This technique is used in drum scanners where a bright image of the work being scanned is focused onto a aperture plate whence it passes thru a small hole onto the photo multiplier tubes.
In principle, you can see, with the unaided eye, a single atom. You just need to illuminate it brightly enough that it reflects or fluoresces enough light in the direction of your eye to see and you also need to do this against a dark background.
Optical Microscope, limit is around 30-40 thousand times. Conventional microscopes hit a max around 1800 times. Royal Raymond built a microscope that reportedly magnified 60,000 times. Gaston Neassens built one around 30-40 thousand times. Current commercially available microscope that is available can resolve down to 50 nm with white light.
Has the mind got limits on scale in imagination? I just tried it, but, unsure how small the image was! Due to the subjective universe being created by the objective universe and imagination being dependent on objective 'seen' objects. ( like the fantasy 'uni corn' being a composite of a 'real' horn and a horse) would the minds of micro biologists, who have knowledge of objects at this scale, be more capable imagining micro objects or beings? I have been thinking about scale for awhile and I'm convinced that relative scale effects time. for example, if we were massive compared to the universe would the big bang be perceived to be like a instant flash, like a firework? but, as the universe is massive relative to us, time is slower and we perceive it to still be happening... sorry, pants at wording thoughts!! I personally feel one draw back to being human is we get locked in to thinking in terms of human scale. Peter J Steadman. (let me dream a life time and i'll be happy), Tue, 1st Apr 2014